The Polygraph Test

What is a Polygraph Test? A Polygraph test will normally take between 2 to 3 hours, sometimes longer and consists of three phases; a pre-test interview, collection of charts, and analysis of charts. Polygraph tests are the most reliable technique to test if someone is being deceptive to a specific issue.

Pre-test interview & formulation of questions During the pre-test interview the examiner will explain how the polygraph works, discuss the issue and develop and review all questions to be asked on the polygraph test. This stage is normally the longest to complete, and can take anywhere between 45 and 90 minutes.

Collection of Charts During this phase the subject will be attached to the polygraph. The set of questions that was developed during the pre-test interview will be asked on several occasions.

Analysis of Charts Once the examiner has collected the polygraph charts he/she will analyse the results before giving a decision as to the subject’s truthfulness or deception to the given issue.

Will I know the questions to be asked on the polygraph examination? Yes! The examiner will construct questions from the information given regarding the test issue. He/She will review the questions with you before testing begins. All the questions should meet the strict rules for the latest polygraph techniques to ensure test accuracy.

All questions are discussed with the subject thoroughly before the test commences and will be answered with a “yes” or “no” answer only.

How reliable is Polygraph Testing? There is no doubt that the polygraph is highly reliable, providing the person using it is properly trained and the technique they use is validated.

How Does the Polygraph Work? The polygraph works by tracing changes in a person’s physiological conditioning during questioning. These changes are recorded directly on to the polygraph charts in order that they can be reviewed. Some of the changes that occur may replicate those that have been linked with truth or deception for many years. These physiological changes have been the subject of various research projects and our examiners have undertaken many hours of polygraph chart analysis instruction to interpret them. The Polygraph charts are generated by attaching four components to the subject.

Pneumograph Two convoluted rubber pneumograph tubes are placed around the subject’s upper chest and abdomen on the outside of their clothing, these record respiration and movement.

G.S.R. The GSR or Galvanic Skin Response is monitored by placing two finger plates across fingers, or two adhesive sensors directly on the hand. These plates trace changes to the skin resistance during the examination.

Cardiosphygmograph This component traces changes to the subjects relative blood pressure and pulse rate and it is similar to the pressure cuff your doctor uses when taking your blood pressure. Alternatively a finger blood pressure cuff may be used.

After the polygraph test has been completed the examiner will read and review the generated charts to establish the test results. The agreed questions will always be asked a minimum of twice before results can be determined.